At least eight people were gunned down by Kenyan police yesterday marking a bloody end to the opposition's street protests against the disputed re-election of President Mwai Kibaki.

In Nairobi's Kibera slum, the home constituency of opposition leader Raila Odinga, seven people were reported to have been shot dead by security officers instructed to prevent demonstrators from reaching a rally venue in the city centre.

A man was also killed in Mombasa when Muslims demonstrated against Kibaki after Friday prayers, bringing the death toll at the hands of police since the start of "peaceful" mass action on Wednesday to more than 20. Odinga's Orange Democratic Movement said that there would be no more demonstrations because too many people - both protesters and bystanders, some just children - were being killed by police.

After displaying restraint during the looting and arson in Nairobi immediately following the December 30 election result, the security forces now appear to be acting under new instructions, venturing deep into the slums to fire teargas and live bullets rather than merely blocking the exit routes using water cannons and shots fired high above the crowds.

A statement signed by nine western countries, including Britain, yesterday expressed concern about the "deteriorating human rights situation", and urged the police, who have admitted killing 82 people over the past three weeks, to "desist from any extraordinary or disproportionate use of force". But the call is likely to have little effect on a regime that is becoming increasingly belligerent towards western countries and domestic critics.

In a series of full-page advertisements this week, paid for by taxpayers, the government accused diplomats, civil society organisations, the UN and the media of waging a "partisan, emotional and personalised campaign against President Kibaki" for calling into question the presidential result.

The advert included a photograph of the British high commissioner Adam Wood. Kenyans for Peace with Truth and Justice (KPTJ), an umbrella organisation of leading local civil society groups, issued a lengthy report detailing the irregularities. It focused on the day leading up to the announcement of the result. It examined the chaotic tallying process at election headquarters, where many people believe rigging took place, and noted that in about two-thirds of the constituencies, the presidential votes cast exceeded the parallel parliamentary count by 325,000 ballots - an unusually high variance that easily exceeds Kibaki's winning margin of 238,000.

While stopping short of saying who had won the election, the KPTJ said that the true result should have been "impossible" to determine due to all the malpractices.